fix(flag_check): never link to avoid false positives

[RubixDev]

Using flag_if_supported when targeting wasm32-unknown-unknown often (or maybe always) results in false negatives, causing supported flags to not be applied. This happens, because clang is trying to link the binary with wasm-ld which must be installed, and even with wasm-ld installed clang still gives me this error:

wasm-ld: error: unknown file type: /lib/crt1.o
wasm-ld: error: cannot open /usr/lib/clang/15.0.7/lib/libclang_rt.builtins-wasm32.a: No such file or directory
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)

This is easily avoided by telling clang to skip linking by using -c.

[thomcc]

Doing this unconditionally does worry me. I do see @dot-asm's arguments for why it's correct, but it is still somewhat worrisome.

I think I'll take this PR, but I wouldn't be surprised if we end up needing to make this conditional again due to issues in the release.